1. Field of the Invention
This invention relates to a DC-DC converter for an electronic flash unit.
2. Description of the Prior Art
Generally, a DC-DC converter is used in an electronic flash unit for boosting the output voltage of a battery to obtain a high voltage flashing energy.
Heretofore, a DC-DC converter of this type has usually been formed with an oscillating transistor, an oscillating transformer, etc. A pnp germanium transistor having a low saturation voltage between the collector and the emitter thereof has been used as the above stated transistor for oscillation. However, germanium transistors are no longer manufactured in substantial quantities. Silicon transistors are now the principal type manufactured. As a result, germanium transistors have become expensive. Hence, there has arisen a strong demand for the use of an npn silicon transistor in place of a pnp germanium transistor. It is not difficult to meet this demand. A mere arrangement whereby a pnp germanium transistor is replaced with an npn silicon transistor would bring about a problem that the operator of the flash unit would tend to have an electric shock in replacing a battery of the flash unit. In the accompanying drawing FIG. 1, a DC-DC converter is shown which is arranged to merely have an oscillating pnp transistor replaced with an npn transistor. For example, when a finger of an operator touches a terminal 16 on the negative pole side of a battery case while another part of the body of the operator is in contact with the case C1 of a camera, an electric charge remaining in a main capacitor 13 is discharged through a winding 7b, the base and the emitter of a transistor 5, a terminal 1a of the battery, the above stated part of the body (which is not shown), the camera case C1, a hot shoe SH and an earth line EL. Thus, with such a simple arrangement, an accident of having an electric shock tends to happen.